1. Field of the Invention
The present invention relates to a pixel and an organic light emitting display including the pixel.
2. Discussion of the Related Art
Recently, various flat panel displays (FPDs) having reduced weight and volume in comparison to cathode ray tubes (CRTs) have been developed. The FPDs include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays.
Among the FPDs, the organic light emitting displays display images using organic light emitting diodes (OLEDs) that generate light by re-combination of electrons and holes. The organic light emitting display has high response speed and is driven with low power consumption.
FIG. 1 is a circuit diagram illustrating a pixel of a conventional organic light emitting display.
Referring to FIG. 1, a pixel 4 of the organic light emitting display includes an organic light emitting diode OLED and a pixel circuit 2 coupled to a data line Dm and a scan line Sn to control the OLED.
The anode electrode of the OLED is coupled to the pixel circuit 2 and the cathode electrode of the OLED is coupled to a second power source ELVSS. The OLED generates light (e.g., light with predetermined brightness) to correspond to current supplied from the pixel circuit 2.
The pixel circuit 2 controls the amount of current supplied to the OLED to correspond to a data signal supplied to the data line Dm when a scan signal is supplied to the scan line Sn. Therefore, the pixel circuit 2 includes a second transistor M2′ coupled between a first power source ELVDD and the OLED, a first transistor M1′ coupled to the second transistor M2′, the data line Dm, and the scan line Sn, and a storage capacitor Cst′ coupled between the gate electrode and the first electrode of the second transistor M2′.
The gate electrode of the first transistor M1′ is coupled to the scan line Sn and the first electrode is coupled to the data line Dm. Then, the second electrode of the first transistor M1′ is coupled to one terminal of the storage capacitor Cst′. Here, the first electrode is one of a source electrode or a drain electrode and the second electrode is the other one of the source electrode or the drain electrode. For example, when the first electrode is the source electrode, the second electrode is the drain electrode. The first transistor M1′ coupled to the scan line Sn and the data line Dm is turned on when a scan signal is supplied from the scan line Sn to supply a data signal supplied from the data line Dm to the storage capacitor Cst′. At this time, the storage capacitor Cst′ is charged with a voltage corresponding to the data signal.
The gate electrode of the second transistor M2′ is coupled to one terminal of the storage capacitor Cst′ and the first electrode is coupled to the other terminal of the storage capacitor Cst′ and the first power source ELVDD. The second electrode of the second transistor M2′ is coupled to the anode electrode of the OLED. The second transistor M2′ controls the amount of current supplied from the first power source ELVDD to the second power source ELVSS via the OLED to correspond to a voltage value stored in the storage capacitor Cst′. The OLED generates light corresponding to the amount of current supplied from the second transistor M2′.
However, according to the conventional organic light emitting display, an image with desired brightness may not be displayed due to a change in efficiency in accordance with the deterioration of the OLED. That is, the OLED deteriorates with the lapse of time so that an image with desired brightness may not be displayed. In practice, as the OLED deteriorates, light with lower brightness is generated.